1. Field of the Invention
The present invention relates to telephony such as that using Voice over Internet Protocol (VoIP). In particular, the present invention relates to integrating Private Branch Exchange (PBX) functionality for a mobile phone in distributed systems using VoIP.
2. Description of the Background Art
A PBX is a telephone exchange that has historically served a particular business office, as opposed to one that a common carrier or telephone company operates for many businesses or the general public. The PBX makes phone call connections among the internal phones of the business and connects them to the public switched telephone network. Each phone in the PBX generally has its own PBX extension number. Generally, this is a four digit number specific to the particular phone. For example, a first phone in the PBX has a phone number “555-555-0001.” The extension for the first phone is the last four digits of this number, “0001.” If a user of a second phone within the PBX wishes to contact extension 0001 then that user merely has to dial “0001” on a keypad of the second phone instead for the full 10 digits. The PBX then connects the call between the first phone and the second phone using internal resources rather than the Public Switched Telephone Network (“PSTN”), avoiding service charges. In contrast, a phone outside the PBX must call 555-555-0001 to connect a call with the first phone.
Another benefit of PBX systems is that they provide the phones connected to the PBX system with the ability to use various enhanced PBX features or functionality such as, but not limited to: (1) call conferencing; (2) placing calls on hold; (3) call parking; (4) call camping; (5) call transferring; (6) call blocking; and (7) music on hold.
In recent years, PBXs have begun to utilize VoIP technology. These PBX systems use the Internet Protocol to carry calls, and typically cost less money due to cheaper hardware, operating costs and maintenance costs. Accordingly, many business have begun using PBX systems utilizing VoIP technology
Another recent trend in business communications is the widespread use of mobile phones. In many businesses, almost all higher-level employees are expected to have a mobile phone. These employees are expected to be available to use their mobile phones up to twenty-four hours a day. Thus, mobile phones are important to business communications. However, a problem with existing PBX systems is that they are unable to integrate mobile phones into the PBX system. As a result, existing mobile phones do not have PBX extensions and cannot utilize PBX functionality.
The prior art has attempted to provide PBX functionality for mobile phones; however, these attempts have been largely unsuccessful and not widely adopted. For example, the prior art has attempted to provide client software that can provide PBX functionality and be loaded onto a mobile phone. One example architecture of the prior art and its disadvantages will be described below with reference to FIG. 1A. This prior art solution suffers from a number of problems. First, it is not available for all mobile phones, and will only work on smart phones. Second, it requires that the user download and activate client software to operate it on the mobile phone. This is cumbersome and difficult for users to accomplish. Third, it is difficult to provide such client software and it is not available for all of phones because there are thousands of different types of mobile phones, with more appearing monthly, each of which needs its own specific client software adapted to its operating system and/or specific functionality provided by that particular mobile phone. Fourth, most mobile networks and mobile phones cannot transmit voice and data simultaneously. As a result, a client application on the mobile phone cannot signal a PBX via the data network when there is an active phone call simultaneously ongoing. Fifth, on some mobile phones, the client application cannot be run when there is an active phone call simultaneously ongoing.
For these reasons, the prior art has not been successful in providing PBX functionality for mobile phones.